Flat pads, spinning pads and rollers: robot mops explained
By Lachlan Ford
"Vacuum and mop" on the box can mean very different things. On one robot it's a damp cloth clipped underneath. On another it's a roller that gets rinsed while it works and washed again when the robot gets home. They suit different houses, so it helps to know which one you're looking at before you get to the rest of the spec sheet.
The short answer
A flat pad wipes, which is fine for dust and footprints. Spinning pads and rollers press down and scrub, so they can shift a mark that has dried on. If you have rugs or carpet, check what the mop does when it reaches them.
How each kind works
The flat pad is the simplest. A cloth pad clips under the back of the robot, a small tank lets water seep into it, and the robot pulls the damp pad along behind it as it drives. Imagine putting a damp cloth under your foot and shuffling across the kitchen. It picks up the fine dust the vacuum left behind, along with fresh footprints, and it does that well enough. Nothing is rubbing, though, so a mark that has dried onto the floor gets a wet cloth passed over it once and is mostly still there afterwards. On some robots the pad shakes rapidly back and forth to add a bit of scrubbing.
Spinning pads are round pads, usually a pair, that sit under the robot and turn while the robot presses them into the floor. The turning is the difference between laying a cloth on a stain and rubbing at it, and it’s what loosens a dried drip of coffee or the ring left by a pot plant.
A roller is a soft cylinder that lies across the robot and turns against the floor, much as a paint roller turns against a wall.
What sets a roller apart is what can happen on the far side of the cylinder. On many roller robots, clean water goes onto the roller and a scraper squeezes the dirty water off again as it comes around, so the strip of roller touching your floor has just been rinsed. A pad, flat or spinning, carries what it has picked up until someone or something washes it.
What the label does and doesn’t tell you
The words “vacuum and mop” cover all three kinds, so they tell you almost nothing. A photo of the robot’s underside will settle it if the spec sheet doesn’t.
The type tells you how the mop moves. It doesn’t tell you how clean the mop stays through a run, and that depends on the dock as much as on the mop. A robot with spinning pads and a washing dock goes home every so often to have its pads rinsed, then heads back out. The same pads on a robot with no washing dock would be wiping the last room with whatever they collected in the first. Our dock explainer goes through this job by job.
You’ll also see a figure for how hard the mop presses down, and one for how far it lifts. The pressing figure is hard to use, because makers quote it in different units and it describes one part of the scrubbing among several. The lift figure is more practical, and it belongs to the next section.
Mops, rugs and carpet
A wet mop and a rug shouldn’t meet, and robots deal with that in a few different ways. The most common is to lift the mop. The robot senses that it has driven onto carpet and raises the pads or roller by a centimetre or so, then lowers them again on the other side. Compare the lift height with your rugs. A low, flat rug passes underneath with room to spare, while a thick one can still brush against a mop that’s lifted as far as it goes.
Some robots go further and leave the mop behind. They drop their pads at the dock before a carpet run and collect them later, and a few roller robots close a cover over the wet roller instead. The Roborock Qrevo Edge 3 Pro shown here does two of these things. It lifts its pads when it reaches carpet, and one setting in its app has it leave them at the dock and vacuum the carpet first.
Where the mop does neither, the job falls to you. Either you mark the rug in the app as a place to avoid while mopping, or you unclip the pad before a vacuum-only run and put it back afterwards. That’s fine once a week, and it gets old quickly if you wanted the robot to mop every day while you’re at work.
In a real house
Daily dust on floorboards is easy work for any of the three, and a flat pad handles it. The kitchen is the harder room. Splashes dry, something sticky gets walked through, and this is where pads that scrub or a roller start to pay for themselves.
Muddy paw prints sit somewhere in between. Fresh ones wipe up with anything, and once they’ve dried they need rubbing. A roller that rinses itself has an advantage on a job like that, because it isn’t carrying the mud from the back door through to the lounge.
Every kind has its limits. A robot mop keeps a reasonably clean floor clean, and it won’t bring back a floor that hasn’t been mopped in a year. Grout lines sit lower than the tile, so a pad or roller passing over the top doesn’t reach far into them.
One thing applies to every kind: a mop that stays wet starts to smell. With a flat pad you take it off and wash it. With pads or a roller, either the dock washes and dries them or you do.
Which one do you need?
If your floors are mostly carpet, the mop hardly matters, and a flat pad or no mop at all will do. If you have a lot of hard floor and a kitchen that gets properly dirty, look at spinning pads or a roller, and treat the dock as part of the same decision. If you have both hard floors and rugs, read the mop lift line on the spec sheet before anything else.
To see how many robots use each kind of mop, check the “In our list” box on this page. Every robot page says which mop it has and whether it lifts, and our guide to robot vacuum mops picks three, one of each kind.
